Wears out at the folds. Same with tents.

I helped repair a fellow cruiser's sail in the Bahamas. His boat had in mast furling and had sat on the hard in the sun for a couple of years before he bought the boat. The first big gust and the sail tore straight up the line where it rubbed up against the mast. Good idea to take your sails off when you put your boat up for a prolonged time.

I was able to patch the rip by machine but a large part of the job had to be done by hand. I lent him my palm.